In integrated circuit chip fabrication, continuous scaling of all interconnect components has necessitated the use of thinner diffusion barriers and higher densities of smaller critical dimension (CD) lines.
The flux of electrons flowing through metal lines in interconnects causes ions to move in a preferential direction leading to voids (opens) and extrusions (shorts). This phenomenon has been termed Electromigration (EM). Electromigration is tied to a number of process steps in backend interconnects. Methods to limit electromigration have been to slow diffusion, impede nucleation, and restricting design rules to damage resistant designs.
Metal line reliability, specifically electromigration, degrades as the length of the lines increases. This may severely restricts the choice of conducting material, diffusion barrier thickness, and length of lines from which the circuit designers may choose.